On Saturday, August 3, 2013 10:21:24 AM UTC-5, sms wrote:
On 8/3/2013 5:10 AM, N8N wrote:



"Far better?" By whose standards? Yours (and even then, you may be deceiving yourself) or oncoming traffic?



Keep in mind that there are some odd perception issues going on with headlamps where a person can honestly believe that his headlights are excellent when they are not optiomal for seeing.



Frank has believed this for years, despite all the evidence to the

contrary, so I have to agree with you there. Except that's only what he

posts here, it's highly likely that he doesn't honestly believe it.

But here's what I really don't understand... you're consistently recommending a flashlight/symmetrical beam for road riding. That's essentially what a car driver would call a "driving light" with a little extra spill around the hot spot - or a light that is actually more tightly focused than a high beam. Great if you're on a deserted country road with nobody else around and traveling at high speed; very much less than ideal anywhere else.

When riding a bicycle, what you really want is something more analogous to an automotive low beam headlamp - throw the light down the road as far as you can without offending other road users, meaning that what you really want is a rectangular or trapezoidal beam pattern with most of the light ending up in a horizontal line right under the cutoff (which should be aimed roughly straight ahead, but a few degrees down) then smoothly decreasing in intensity back towards you - so that from your perspective the road is illuminated with relatively even intensity. Too much foreground light can actually lull you into a false sense of security about your lights, thinking that they are better than they are, as they illuminate the road that you're just about to travel over really well, while perhaps not putting enough light out a few seconds ahead of you, where you really need to be looking. (this is exactly what I was alluding to in my previous post odd perception issues.)

A little light above the cutoff is desirable to read road signs, identify obstacles, display your presence to other road users, etc. (as has been thrashed to death in the other thread) but in practice designers try to minimize this as much as possible and even so there's always enough light above horizontal to accomplish these goals.

Unfortunately when it comes to bicycle lighting in the US, it seems like most of the products developed have been aimed toward the MTB crowd so we have ultra-high-power symmetrical beam lights with no thought at all given to on road use. Whereas in Europe, where bicycle commuting seems to be more common, there are actually regulations in place designed to make sure that the lights being used are considerate to other road users.

Now I've probably given the impression that I consider StVZO lights to be the be-all and end-all of bike lights. I don't - those regulations artificially limit the amount of light able to be thrown out on the road by the 2.7W restriction for dynamo lights. Certainly more power could be used, but by the regs it is not. So the light designers, working under that constraint and the constraints of the available LED emitters, have to make some compromise - either they tighten up the beam pattern from what is optimal to put good light in the areas that are lit, or they produce a good beam pattern but not as much light as they could. However, I have hope that with increasingly more efficient LED emitters we may see in a few years really, really good StVZO headlights that one could use without feeling that any compromises were made at all (although we may actually have them and I just haven't tried them yet, being about 5 years behind in my own lighting purchases. e.g. the new B&M and Philips lights are apparently quite a bit better than anything I've used.) The reason that I am partial to StVZO lights, however, is it seems that in the current market one has to make a choice between StVZO and symmetrical beam lights as there just aren't any other options available, so StVZO it is as those lights come closer to the ideal beam pattern for on-road than any others available.

Now for a dual beam setup, yes, a flashlight type beam is great for a "high beam" or off road light, although for typical bicycle speeds (almost never exceeding 30 MPH unless you're in far better shape than YT) I'd say that a lot of flashlights that I've seen could use to have less focus and a larger hot spot to be more usable for that use.

nate